The present invention relates to a device and a method for repairing pipe, such as underground sewer pipe and the like.
Prior methods for repairing damage to pipelines include moving a liner tube impregnated with a liquid material capable of curing and hardening to a position within the pipe where the damaged portion is located. An inflation bladder is often used to urge the liner tube in a outward radial direction into contact with the pipe being repaired and a liquid material impregnating the liner tube is permitted to cure and harden. The liner tube is installed by pulling, pushing or everting the liner into the host pipe. Once the liner is positioned within the host pipe, it is pressurized, usually by an inflation bladder, causing the liner to press against the interior wall of the host pipe, and the liner is cured by applying heat, such as steam or hot water. These liners can also be cured at ambient temperatures by a chemical mixture which generates an exothermic reaction. The liner tube forms an interior liner in the pipe for the pipeline being repaired. Such a process is known as cured-in-place pipelining.
On some occasions lateral pipes are connected to main pipes. Often damage occurs at the junction between the lateral pipe and the main pipe, which is regarded as one of the weakest points in a sewer system. T-shaped or Y-shaped liner tubes have been utilized to fit within the junction between the lateral and main pipes. Liner tubes form a T-shaped or Y-shaped liner after hardening to the interior of the junction between the pipes. Again, inflation bladders are typically used to pressurize the liners against the interior walls of the host pipes.
To ensure that the liner is open ended, the inflation bladder normally extends some distance beyond the liner tube. For example, the bladder tube may extend a foot beyond the liner tube. Pressures may range between approximately 5 and 30 PSI within the inflation bladder during an evertion process where the liner transitions from inside the bladder to outside the bladder.
The portion of the inflation bladder that is not contained by the liner or host pipe creates a weak point in the system. Where the bladder is contained by the liner or host pipe, it can withstand more pressure before bursting or failing. The weak points in the system where the bladder is not contained by the liner effectively limit how much pressure you can put in the inflation bladder before the bladder will burst, which is known as the burst pressure or failure point. Also, the closed end of the bladder and points where the bladder is connected to a launching device are weak points where the bladder is prone to burst.
FIGS. 1 and 2 illustrate a prior art device and method of lining the junction between a main pipe 10 and a lateral pipe 12. The liner/bladder assembly shown includes a lateral liner tube 14, a main liner tube 16, a lateral bladder tube 18, and a main bladder tube 20. The liner/bladder assembly is positioned about a launching device 22. Once the launching device 22 is in an operable position in the main pipe 10 adjacent the opening to the lateral pipe 12, the lateral bladder tube 18 and lateral liner tube 14 are everted into the lateral pipe 12 and the main bladder tube 20 is inflated to press the main liner tube 16 against the main pipe 10. The main and lateral bladder tubes 20, 18 are pressurized using a fluid, such as air, steam or hot water.
As shown in FIG. 2, portions A of the lateral bladder tube 18 and portions B of the main bladder tube 20 refer to weak points in the system where the bladder tubes are not contained by the main and lateral liner tubes 16, 14. These unrestrained locations of the bladder tubes limit how much pressure can be applied within the bladder tubes.
There is therefore a need in the art for a device and method of renewing a pipeline that eliminates or reduces the number of weak points in the system when the inflation bladders are pressurized. There is also a need in the art for a device and method that allows greater pressure to be applied within the inflation bladder without bursting the bladder.